HP OpenVMS Systems

Increasing available disk storage?

We have a DS20 with single process and RAID 5.
With five 9 GB drives: 3 data drives, 1 hotswap, 1 parity drive so total of
27GB storage.
How can we add more storage space, like say double the space?? I know that we
can go SAN, but it is little too much for the amount of space we have. Do you
have products like the SAN but just use SCSI connection?? Can that storage
device be share with N
T server file server?
thanks
Jim Wong